I'm running into a StackOverflowException (please don't ask, it's not my fault) in IIS6/2k3 which has a limit of 256k, but the exception doesn't happen in the VS debugger.
As a matter of understanding I'd love to know, but have failed to google what the stack limit of Cassini is...if indeed it has one?
Have you tried stack-overflowing Cassini on purpose to see at what point it crashes? I'd imagine the stack is immense, though I would expect Cassini to replicate IIS as closely as possible. It's surprising that something that runs in VS wouldn't run in IIS, and I'd even consider filing a VS bug with Microsoft, since it seems that the whole point of Cassini is to replicate the functionality of IIS and provide an ideal debugging environment, since any web projects you write in VS will inherently be deployed against IIS.
I'm not sure if this forum thread was posted by you, or if you've seen it, but he seems to have the exact same problem, in case you're still experiencing it.